1. Field of the Invention
The present invention relates to a power semiconductor module, in particular a power semiconductor module preferred for a power conversion unit that converts DC power into AC power or AC power into DC power.
2. Description of Related Art
A power conversion unit includes a function to convert DC power supplied from a DC power supply into AC power so as to supply AC power to an AC load such as a rotating electrical machine or a function to convert AC power generated by a rotating electrical machine into DC power so as to supply DC power to a DC power supply.
To serve such conversion function, the power conversion unit includes an inverter having a semiconductor device with a switching function, and, by repeating conduction and interruption of the semiconductor device, power conversion is performed from DC power to AC power or AC power to DC power.
The switching semiconductor device generates heat upon switching or upon energization. Due to this, the semiconductor device is mounted on a high thermal conductivity member to form a heat dissipation structure.
In particular for reducing the power conversion unit in size and cost, it is desirable to adopt a high heat dissipation structure and to reduce the area of the semiconductor device.
Japanese Laid Open Patent Publication No. 2008-259267 discloses a structure in which both sides of a semiconductor device are soldered to a high thermal conductivity member so that heat is dissipated through the both sides of the semiconductor device.
In addition, EP1467607 discloses a structure in which cylindrical metal is soldered on a chip and a metal plate is soldered on a top surface of the metal soldering so that heat is dissipated through both sides of a semiconductor device.
In addition, Japanese Laid Open Patent Publication No. 2000-349207 discloses a structure in which a Si chip is sandwiched by a jointing member and a heat sink so as to suppress thermal stress based upon a difference in coefficient of thermal expansion.
However, the stress was not sufficiently reduced inside the power semiconductor module and thus reliability was not sufficiently ensured.